1. Field of the Invention
The present invention relates to a suspension for supporting a magnetic head slider for reading and/or writing data from and/to a recording medium such as a hard disc device.
2. Related Art
In recent years, data storage devices for reading and/or writing data from and/to recording mediums through a magnetic head slider have been widely used in mobile apparatuses such as notebook-type personal computers and portable music players and, along therewith, these data storage devices have been required to have high impact resistance.
More specifically, when such a data storage device is subjected to an external impulsive force with an acceleration equal to or greater than a certain value in such a direction that the magnetic head slider is separated from a disk surface, the magnetic head slider jumps in such a direction that it separates from the disk surface and, then, swings back from the jump to the disc surface and impinges on the disk surface, thereby damaging the disk surface. Accordingly, in order to increase the impact resistance of the data storage device, there is a need for raising the value of the acceleration (the critical acceleration) of an external impulsive force which triggers jump of the magnetic head slider.
For example, by increasing the load which presses the magnetic head slider against the disk surface, it is possible to raise the critical acceleration.
However, it is necessary to set the load to within a proper range, in order to control the height of the magnetic head slider above the disk surface. Accordingly, there is naturally a limit to the method which increases the load for suppressing the jump of the magnetic head slider.
As another structure for suppressing the jump of the magnetic head slider, there is also known a structure in which the mass of a load beam portion is reduced for reducing the inertial force applied to the load beam portion when an impulsive force is applied thereto, thus raising the critical acceleration.
However, when the thickness of the load beam portion is reduced and/or a hole is formed in the load beam portion in order to reduce the mass of the load beam portion, this will reduce the rigidity of the load beam portion, thus inducing the problem of degradation of the vibration characteristics and the loading/unloading characteristics.
As still another structure for suppressing the jump of the magnetic head slider, there has been proposed a structure in which the load beam portion supported through a load bending portion by a supporting portion such as an arm or a base plate is formed to have an extending portion extending toward the base-end side of the suspension (for example, JP-A. No. 9-082052, JP-A. No. 11-039808, JP-A. No. 2004-348804, and JP-A. No. 2005-174506).
The conventional structure is configured so as to makes the mass of the portion of the load beam portion which is closer to the base-end side of the suspension than the load bending portion to be as equal as possible to the mass of the portion thereof which is closer to the tip-end side of the suspension than the load bending portion. The structure is advantageous in suppressing the jump of the magnetic head slider at a time when being subjected to an external impulsive forced without degrading the rigidity of the load beam portion.
However, in the magnetic head suspensions described in these patent documents, the load beam portion is connected to the free end portion of the load bending portion which is supported by the supporting portion in a cantilever manner. With these structures, the supporting point of the load beam portion (namely, the portion of the load beam portion which is connected to the load bending portion) may vary in the direction orthogonal to the disk surface when an impulsive force is applied thereto.
Accordingly, the magnetic head suspensions described in these patent documents can not sufficiently raise the critical acceleration, although the problem of degradation of the rigidity of the load beam portion does not occur.